Substantial research, development and other efforts have been devoted to the development of efficient and environmentally friendly energy harvesting devices. Photovoltaic technology is one of the most prominent sustainable energy technologies, and accordingly, substantial sustainable energy research advancements have been made in this technology area. However, energy harvesting devices based on photovoltaic technologies have typically had relatively low conversion efficiencies (e.g., approximately 50% conversion efficiency). Also, devices based on photovoltaic technologies are typically relatively expensive.
Photovoltaic technology also does not have the capability to take advantage of a substantial area of the solar spectrum, since photovoltaic technology is only able to harvest the visible sunlight. For example, the earth receives more than 100 petawatts (i.e., 100×1015 watts) of solar power that cover different spectrums ranging from infrared to visible waves. Solar power accounts for a substantial amount of the power that penetrates the atmosphere in forms of infrared energy. More specifically, solar power accounts for electromagnetic radiation of over one kilowatt per square meter that reaches sea level, approximately half of which is infrared radiation. Infrared spectrum that extends from approximately 1 millimeter (mm) to approximately 1 μm is located between the radio and visible regimes. At 10 micrometer (μm) wavelength, the atmospheric transmittancy reaches approximately 80%, which means a substantial amount of infrared radiation reaches to the earth at sea level. Photovoltaic technology also does not have the capability to take advantage of a substantial area of the solar spectrum, since photovoltaic technology is only able to harvest the visible sunlight.
Antenna-based energy harvesting techniques, on the other hand, leverage solar energy from non-visible radiation. In antenna-based energy harvesting techniques, attention has typically been focused on harnessing solar energy using classical antennas, by which electromagnetic waves can be confined and directed to an intended load. For solar energy harvesting, a nanoantenna is not only able to harness the visible light, but it can be properly scaled to collect infrared radiation as well. A square spiral antenna is an example of an antenna-based energy harvesting device. An example conventional square spiral antenna typically operates at a frequency of approximately 28.3 THz and has a total length of approximately 10.6 μm.
Typically, power harvesting using conventional collectors (e.g., classical antennas or radiators) do not provide a highly efficient energy harvesting, are complex to manufacture and design, and have destructive coupling issues.